See extraordinary artist Stephen Wiltshire on a special "Super Humans" edition of "20/20" Friday at 9 p.m. ET

Wiltshire was late to develop speech. It wasn't until he was 5 years old that he spoke his first word: "paper." "Well, because I needed some paper to draw on, so I asked my teacher about it," he said. His second word was "pen." He's been drawing ever since.

Wiltshire has spent the past 25 years traveling the globe, observing some of the world's most monumental structures and scenes -- in London, Tokyo, Dubai, Venice, Sydney, San Francisco and Hollywood. But no city is more special to him than New York. "I've been there about three times this year. The buildings are so tall. Very tall skyscrapers. Squared avenues. And yellow New York taxis," he said.

Wiltshire's drawings have a whimsical feel while maintaining precise detail, and it may be a lifelong disorder that is the secret strength behind his talent.

The Science Behind an Extraordinary Artist
Wiltshire is autistic, and his struggle with communication may be the reason for his artistic success, explained Dr. Geraldine Dawson, chief science officer at Autism Speaks, and research professor of psychiatry at the University of North Carolina at Chapel Hill.

"Autism is a neural developmental condition that shows up early in life. It involves difficulties in the area of social interaction, with reading facial expressions, with forming peer relations -- overall, difficulties in communication," Dawson said.

"There are many challenges that are associated with autism. There also are many unique strengths.
Stephen is one of those people with autism who does have a special talent in art, and also his visual memory is really exceptional," Dawson said.

Autism impairs communication among certain parts of the brain, which severely affects the brain's ability to process information. But these roadblocks may help Wiltshire focus on the details in his drawings.

"The person with autism tends to be able to use those lower perceptual areas independently, and they don't have the interference with some of the language areas and other higher areas that seem to interfere with their ability to see and reproduce a visual scene," Dawson said.

Someone without autism may have a lot of wondering thoughts: Why are those buildings so close together? Why is that tiny one squeezed in with those tall ones? I wonder where a good place to eat is down there? while Wiltshire can focus effortlessly on the details alone.

"When we view people like Stephen, and we see the special abilities that they have, it really shows us that our brains have an amazing capacity that perhaps most of us can't tap into, and so it does teach us a lot about the remarkable capacity of the human mind," Dawson said.

When Wiltshire sees a landscape, he can remember it, not for a while but forever, recalling it from memory like a tourist with a digital camera.

Wiltshire's Drawings Bring Happiness

Dawson pointed out that while this visual memory is a rare gift, Wiltshire's art is something he has had to work at. "The exceptional talent not only comes from the natural inborn abilities but also spending hours and hours practicing that skill."

But everyday life for Wiltshire can pose difficulties. Now 37, he still lives with his mother. His sister runs his business. Wiltshire's autism makes relationships and communication very hard, but he appears to realize the happiness his drawings bring to people.

"They say to me, they use that word genius. In Russian, 'genii.' I remember that sometimes," he said. When asked by ABC News' Nick Watt, "Do you think you're a genius?" Wiltshire offers a sheepish smile and the answer, "Yeah, I am. Of course."

A genius -- and an inspiration to others with autism.

"When people like Stephen can develop their talents, and even use those talents to have a profession where they can earn money, this is a great role model for other young people with autism who can hopefully look up to people like Stephen and say, you know, 'I can do that too,'" Dawson said.